1. Field of the Invention
The invention relates to a surgical instrument, and more particularly relates to a trocar assembly.
2. Description of the Prior Art
Trocars are basically sharp-pointed surgical instruments which are used to puncture a body cavity. This is often done so that fluids may be drained from the body cavity using a cannula inserted into the puncture opening, or the cavity may be examined using an endoscopic instrument in accordance with insufflatory surgical techniques.
Two conventional trocar assemblies are disclosed in U.S. Pat. No. 4,654,030, which issued to Frederic Moll et al. and in copending U.S. patent application Ser. No. 920,509 filed Oct. 17, 1986. The trocar assembly disclosed in the Moll et al. patent includes an obturator having a sharpened tip at one end for piercing a body cavity, and a hand grip portion mounted on the other end of the obturator which the surgeon grasps in the palm of his hand.
Conventional trocars have their obturators secured to the hand grip so that the obturator cannot rotate separately from the hand grip. For example, the trocar assembly disclosed in the Moll et al. patent has a triangular-shaped depression 32 formed in the hand grip 14, which depression receives the triangular-shaped end of the obturator to prevent the obturator from rotating relative to the hand grip during use.
It has been found that use of a trocar assembly in which the obturator cannot rotate independently of the hand grip may cause unnecessary trauma to the body cavity tissue, which would be avoidable if the obturator were rotatably mounted on the hand grip. This is because a considerable force is usually required to thrust the trocar through the body cavity wall. When applying this force, the surgeon very often will inadvertently twist or turn the trocar. The rotation of the trocar effects a grinding or drilling action of the obturator's piercing tip, which tears the tissues surrounding the puncture opening and traumatizes the wound.